1. Field of the Invention
The present invention generally relates to overload relays to be combined with contactors. Such overload relays are located in series between a contactor and the electrical load to be switched and protected against overload. The present invention relates in particular to overload relays with thermally delayed overload tripping, with magnetic short circuit tripping, or with a combination of the two types of tripping, but also to overload relays equipped with current transformers. A typical area of application is in the protection of motors.
2. Background Information
Such an overload relay to be combined with a contactor, with bimetal trip elements for each current phase to be protected, is disclosed in French Patent 2 625 603 A1. This overload relay, on the side toward the contactor, has non-withdrawable plug-in connectors, as phase connectors. These plug-in connectors can be connected to terminal clamps of the contactor. For this purpose, on one hand, the plug-in connectors are designed so that they will be compatible, in terms of phase separation and phase height (i.e. in terms of the connection geometry) with the terminal clamps of the contactor, and on the other hand, the overload relay can be snapped onto the contactor. On the side toward the load, the overload relay has non-withdrawal terminal clamps as phase connectors. The terminal connectors of the overload relay do not tend to have the same connection geometry as the terminal connectors of the contactor, which complicates matters for the user in terms of design, installation, service and maintenance. The scope of application is also limited to combinations with contactors of the same structure and size. Employing this solution, it is generally impossible to use the components for individual mounting or installation as isolated units.
Siemens Catalogue NS 2/1991 (Pages 4/13 and 11/7, 8, 23) shows that a thermally delayed overload relay 3UA60, on the contactor side, has non-withdrawable, flat-type plug-in connectors which are compatible with the relay-side terminal connectors of a 3TF50 contactor to be connected to it, and contains additional means for snapping onto a top-hat rail, or DIN rail, or for bolting to a mounting plate. The load-side terminal connectors of the overload relay have the same connection geometry as the relay-side terminal connectors of the contactor, which makes them easier to use. This solution also makes it possible to mount the components individually, because they can be inserted into a relay base 3UX1 424 designed as a box terminal package by means of the plug-in connectors of the overload relay and connected to the latter, to make possible the connection of the phase conductor. In an additional combination of a 3TF51 contactor and a 3UA61 overload relay, the overload relay has flat-type connectors on both sides, which have holes for screw connections and are compatible with the flat-type connectors of the contactor in terms of their connector type and geometry. But a disadvantage of these solutions is that it is difficult or impossible to combine the overload relays with contactors which have different connector types and geometries. There are comparable problems with regard to different phase conductors departing from the overload relay and leading to the load.
As indicated in KLOCKNER-MOELLER-POST, Volume 89, April 1976, pages 27-32, an overload relay equipped with load-side terminal clamps is designed as a basic unit, to which can be bolted a contactor-side terminal block designed as a non-enclosed elbow-coupling component, the height of which can be adjusted within certain limits. The elbow-couplings are plug-in connectors, which make possible a direct connection with a contactor--but only if the contactor is equipped with terminal clamps. The overload relay can only be fastened to a mounting plate by means of the basic unit. The availability of different terminal blocks makes it possible to adapt the contactor side of the overload relay to contactors of a series having a different phase geometry--but not for the load side of the overload relay. For individual mounting of the overload relay, there is a terminal block which has clamp connectors.
German Patent 84 34 232 U1 also discloses an overload relay which consists of a basic unit with load-side clamp connectors and a contactor-side, enclosed terminal block. The terminal block is electrically connected to the basic unit by means of detachable plug-in connectors, and is mechanically connected to the basic unit by means of locking connections. The overload relay can be individually mounted using a terminal block equipped with clamp connectors. By using a terminal block equipped with plug-in connectors, the overload relay can be directly combined with a contactor, but only if the contactor is equipped with clamp connectors. By means of an appropriate crimping, or offsetting, of the plug-in connectors, the overload relay can also be connected to contactors with different phase separations. The load-side of the overload relay is also compatible with regard to the phase separation of a contactor--but a load-side adjustment to contactors with different phase separations is essentially not possible. The overload relay, as such, can essentially only be fastened to a mounting plate by means of the basic unit. The plug-in connection between the basic unit and the terminal block tends to make the overload relay unsuitable for use in high-intensity current applications.